1. Field of the Invention
The present invention relates to a three-dimensional image display apparatus for displaying a three-dimensional image.
2. Description of the Related Art
As a three-dimensional image display apparatus capable of displaying an animation, i.e., a so-called three-dimensional display, various types are known. In recent years, a system of a flat panel type and requiring no dedicated spectacles or the like is strongly demanded. As a three-dimensional image display apparatus of the type that requires no dedicated spectacles, there is an image display apparatus of a system utilizing the principle of holography. In this system utilizing the principle of holography, displaying a three-dimensional full-color moving picture is considered to be difficult. In contrast to the system utilizing the principle of holography, there is a system in which a light ray control element is set just in front of a display panel (display apparatus) in which pixel positions are fixed like a liquid crystal display apparatus of a direct-view-type or a projection type, or a plasma display apparatus, and light rays from the display panel are controlled to be directed to the observer. According to this system, a three-dimensional full-color moving picture or video can be displayed with relative ease.
The light ray control element is also called a parallax barrier, in which light rays are controlled in such a manner that even when the same position area on the light ray control element is observed, different images can be seen depending on the angle at which the position is observed. More specifically, when only left-right parallax (horizontal parallax) is to be given, a slit or a lenticular sheet (cylindrical lens array) is used as the light ray control element, and when vertical parallax is to be applied in addition to the horizontal parallax, a pinhole array or a lens array is used as the light ray control element.
The system using the parallax barrier is further classified into several types, i.e., a two-eye type, multi-eye type, ultra-multi-eye type (extremely multi-eye type), and integral imaging (hereinafter referred to also as II) type. In the two-eye type, holoscopic vision is realized on the basis of binocular parallax, the three-dimensional image of the multi-eye type and those subsequent thereto are accompanied by movement parallax to a greater or lesser extent, and hence they are called three-dimensional images as distinct from the two-eye type holoscopic image. The fundamental principle for displaying these three-dimensional images is substantially the same as the principle of integral photography (IP) invented about one hundred years ago and applied to the three-dimensional photograph.
Among these systems, the II system has a feature that it is high in the freedom of the eyepoint position, and holoscopic vision is easily enabled. In the one-dimensional II system in which only horizontal parallax is enabled and the vertical parallax is removed, as described in SID04 Digest 1438 (2004), a display apparatus having a high resolution can be realized with relative ease. On the contrary, in the two-eye system or multi-eye system, the resolution can be enhanced easier than the one-dimensional II system by limiting the eyepoint positions at which holoscopic vision is enabled, and a three-dimensional image can be created by only images obtained from the eyepoint position, whereby the load for preparing an image can be lowered. Instead, since the visual field is limited, there is the problem that the viewability is poor.
In such a direct-view-type naked eye three-dimensional display apparatus using a slit or a lenticular sheet, there is the problem that a periodic structure of the opening of the light ray control element in the horizontal direction (first direction) and a periodic structure of a non-display section provided on the flat display device in a matrix form so as to allow the pixels to be separated from each other or a periodic structure of the color arrangement of the pixels in the horizontal direction (first direction) optically interfere with each other, whereby moire fringes or color moire are liable to occur. As the measures for this, a method is known in which the periodicity of the light ray control element is slanted, i.e., the lens is slanted. In this method, however, straight lines extending in the vertical and horizontal directions are displayed in a jagged form, and hence, particularly, there is a problem that the text display quality is poor. In a vertical lens in which a lens characteristic is not provided in the vertical direction (second direction), and the periodicity is limited to the horizontal direction, although the text display quality does not become a problem, in order to resolve the color moire, the color arrangement of the flat display device must be a mosaic arrangement or a lateral stripe arrangement. Furthermore, in order to resolve the problem of the moire caused by the interference of the periodic structure of the opening area 1 of the light ray control element in the horizontal direction with the periodic structure of a non-display section provided on the flat display device in a matrix form so as to allow the pixels to be separated from each other, as disclosed in JPA No. 2005-86414(KOKAI), by interposing a diffusion film or the like between the flat display device and the lenticular sheet, light rays from sub-pixels adjacent to each other in the horizontal direction are merged into each other, thereby removing the periodicity in the horizontal direction and resolving the problem of the moire. However, when the diffusion film is added, a problem occurs that external light is dispersed and the contrast in a lighted environment is lowered.
As methods other than the method of using the diffusion film for appropriately merging the light rays from sub-pixels adjacent to each other into each other, a method in which the arrangement of the sub-pixels is a delta arrangement as disclosed in JP3027506, a method in which an opening part of a sub-pixel is formed into a parallelogram so as to allow pixels adjacent to each other in the horizontal direction overlap with each other on a coordinate in the horizontal direction as disclosed in WO97/02709, and a method in which a total value of opening area lengths of sub-pixels in the vertical direction (second direction) is not varied in the horizontal direction as disclosed in JP3525995 are known. However, in a design conforming to JP3027506, it is necessary to provide a gate line continuous in the vertical direction, and hence there is a problem that the numerical aperture is equal to 50% or lower. Further, as disclosed in WO97/02709, if sub-pixels are arranged such that the barycenter of each of them is not shifted in the vertical and horizontal directions while the opening area shape is formed into a parallelogram, there is a problem that it becomes difficult to arrange a signal line to be normally provided continuously in the vertical direction.
Further, in order to realize a simple opening area shape shown in JP3525995, there occurs a need to additionally provide a the light shielding section 3 in addition to light shielding elements such as thin-film transistors (TFTs) and Cs lines provided locally in each of sub-pixels 10 of the LCD.
As described above, in the conventional three-dimensional image display apparatus, in which the light ray control element having the periodicity limited in the horizontal direction (first direction) and the flat display device having pixels arranged in a matrix form are combined with each other, the periodicity of the light ray control element in the first direction and the periodicity of the flat display device in the horizontal direction interfere with each other, and unevenness in brightness (moire) is caused. As a method for resolving the problem of the moire, there is a method in which the opening area length in the second direction (vertical direction) is made constant, and the opening area length in the second direction is made not to vary in the first direction, i.e., the periodicity of the opening area length in the second direction is eliminated. If it is attempted to satisfy this condition while providing the structure in which coordinate points in the first direction having TFTs, Cs lines, and shielding of poor orientation of liquid crystals are locally present, dummy the light shielding sections which are normally unnecessary must be provided such that the opening area length in the second direction becomes constant in the first direction in addition to the light shielding sections which are originally necessary, thereby posing a problem that the numerical aperture is lowered.